Here we use OSSEs configured as a "twin experiment", where we perform the same experiment with both HUXt and SIR-HUXt, to assess the performance of the SIR scheme relative to an ensemble of HUXt simulations without data assimilation. This is the same general method as that employed by [1]}, who investigated the use the Local Ensemble Transform Kalman Filter with the WSA-ENLIL solar wind model, and in [2]}, in the development of the Burger Radial Variational Data Assimilation with the HUX solar wind model.
